JP2008046401A - Sheet material separating device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sheet material separating device capable of preventing the damage of a fixing roller, and to obtain an image forming apparatus that is equipped with the sheet material separating device. <P>SOLUTION: A stiff sheet material P conveyed from the fixing roller 38A, while the tip part thereof is floating on the surface of the fixing roller 38A is separated by a separation guide 66 from the fixing roller 38A, and is then conveyed upward. That is, the sheet material P such as a stiff cardboard, with a floating tip part, is separated from the fixing roller 38A by the separation guide 66, arranged leaving a gap from the fixing roller 38A, consequently, the tip part floating on the fixing roller 38A of the sheet material P does not collide with a separation claw 64. Even if the tip part, floating on the fixing roller 38A of the sheet material P, collides with the separation guide 66, vibration resulting from the collision force will not reach the surface of the fixing roller 38A, by arranging the gap between the fixing roller 38A and the separation guide 66. In this way, damage to the fixing roller 38A can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet material separating apparatus and an image forming apparatus including the sheet material separating apparatus.

  In the case of a heat fixing roller type fixing device, the fixing roller rotates with the tip of the separation claw for separating the sheet material after fixing from the fixing roller always in contact with the fixing roller. The surface layer of the fixing roller that is present may be partially worn or damaged. As a result, there is a problem that the performance cannot be maintained until the life of the original fixing roller, and the life of the fixing device is shortened.

As a technique for preventing such partial wear and damage, there is a fixing device that provides a gap between the tip of the separation claw and the surface of the fixing roller by bringing a convex portion provided inside the separation claw into contact with the fixing roller. Proposed. (Patent Document 1)
According to this, it is possible to prevent rotational wear of the surface layer of the fixing roller due to the tip of the separation claw hitting the surface of the fixing roller.
JP-A-5-107978

  However, in the actual separation of the sheet material, not all the sheet materials are separated from the fixing roller by the separation claw, but may be separated from the fixing roller naturally by the strength of the sheet material itself. Particularly in the case of thick paper and the like, there is a problem that the leading edge of the sheet material collides with the separation claw, and this collision force causes the leading edge of the separation claw to bite into the fixing roller, causing damage to the fixing roller.

  In recent years, the demand for printing on special sheet materials such as thick paper and postcards, which are particularly stiff, has been increasing, and it is considered that damage to the fixing roller is accelerated.

  An object of the present invention is to prevent damage to the fixing roller in consideration of the above facts.

  According to a first aspect of the present invention, there is provided a sheet material separating apparatus comprising: a pressure member that pressurizes a sheet material; and a fixing roller that forms a nip portion with the pressure member and heat-fixes a toner image on the sheet material. A sheet material separating device provided in the fixing device, wherein the separation claw contacts the fixing roller and separates the sheet material from the fixing device, and the fixing roller and a gap are provided between the separation claw and the nip portion. And a plate-like separation guide arranged.

  According to the above configuration, the pressure member and the fixing roller sandwich and convey the sheet material on which the toner image is formed at the nip, and heat-fix the toner image on the sheet material.

  Here, the separation claw in contact with the fixing roller separates the sheet material in close contact with the fixing roller from the fixing roller by melting the toner.

  In addition, the separation guide arranged with a gap from the fixing roller separates the stiff sheet material, the tip of which is lifted from the fixing roller, from the fixing roller.

  That is, the leading end of the sheet material that has floated from the fixing roller does not collide with the separation claw. Even if the leading edge of the sheet material floating from the fixing roller collides with the separation guide, the vibration due to the collision force reaches the surface of the fixing roller due to a certain gap provided between the separation guide and the fixing roller. do not do.

  Therefore, partial damage of the fixing roller due to the collision of the sheet material with the separation claw can be prevented.

  The sheet material separating apparatus according to a second aspect of the present invention is characterized in that, in the first aspect, the separation guide is formed with a convex portion toward the upstream side in the conveying direction of the sheet material.

  According to the above configuration, since the convex portion is formed in the separation guide, the sheet material can be gradually separated from the convex portion, and a paper jam in the separation of the sheet material by the separation guide can be prevented. .

  The sheet material separating apparatus according to a third aspect of the present invention is the sheet material separating apparatus according to the second aspect, wherein the convex portion is formed at a central portion in the rotation axis direction of the fixing roller.

  According to the said structure, since the convex-shaped part is formed in the center part of a rotating shaft direction, a sheet | seat material can be isolate | separated with sufficient balance.

  The sheet material separating apparatus according to a fourth aspect of the present invention is the sheet material separating apparatus according to the second or third aspect, wherein the convex portion has a triangular shape.

  According to the said structure, since a convex-shaped part is triangular shape, a sheet | seat material can be smoothly isolate | separated along a triangular hypotenuse.

  An image forming apparatus according to a fifth aspect of the present invention includes the sheet material separating device according to any one of the first to fourth aspects.

  According to the above configuration, since the image forming apparatus includes the sheet material separating device according to any one of claims 1 to 4, even if a stiff sheet material is used, a partial fixing roller is used. Damage can be prevented and the life of the fixing device can be extended.

  According to the present invention, partial damage of the fixing roller due to the separation claw can be prevented.

  An embodiment of an image forming apparatus provided with a sheet material separating device 44 of the present invention will be described with reference to FIGS.

  As shown in FIG. 5, the image forming apparatus 10 includes a housing 12 as a casing, and a developing device 24Y that forms a yellow toner image in the housing 12, a developing device 24M that forms a magenta toner image, and cyan. A developing device 24C for forming the toner image and a developing device 24K for forming the black toner image are arranged in the vertical direction in order from the top. In addition, when it is necessary to distinguish YMCK, it demonstrates by attaching | subjecting any one of Y, M, C, and K after a code | symbol, and when it is not necessary to distinguish YMCK, YMCK is abbreviate | omitted.

  On the other hand, the photosensitive member cartridge 18 disposed above the developing unit 24 includes a drum-shaped photosensitive member 22 and a charging roller 26 that charges the surface of the photosensitive member 22. Further, an optical scanning device 14 corresponding to each color for exposing the surface of the photoconductor 22 to form an electrostatic latent image is disposed adjacent to the photoconductor cartridge 18.

  Further, the developing rollers 20 provided in the developing devices 24Y, 24M, 24C, and 24K respectively convert the electrostatic latent image on the photosensitive member 22 to yellow (Y), magenta (M), cyan (C), and black (K). Visualize by developing with toner.

  Further, a transfer roller 30 for transferring the toner image of the photosensitive member 22 to the sheet material P is disposed to face the photosensitive member 22, and constitutes an image forming unit 60.

  On the other hand, a sheet feeding cassette 16 that accommodates the sheet material P is provided in a lower portion in the housing 12. The sheet feeding cassette 16 is provided with a feed roller 32 that feeds the sheet material P at a predetermined timing, and a sheet material P conveyance path 28 positioned between the feed roller 32 and the developing device 24K has a nip. A conveyance roller 34 is provided, and an optical sheet material passage sensor 36 is disposed on the downstream side of the nip conveyance roller 34.

  The sheet material passage sensor 36 detects the leading edge of the sheet material P, and the electrostatic latent image writing timing of each optical scanning device 14 is controlled based on the detection timing. Further, a fixing device 38 for fixing the toner image to the sheet material P by heating and press-bonding is provided in the transport path 28 located on the downstream side of the developing device 24Y. The inside of the housing 70 of the fixing device 38 is provided. Are provided with a fixing roller 38A and a pressure roller 38B with a built-in heater. Details of the fixing device 38 will be described later.

  On the downstream side of the fixing device 38, a guide member 48 and a discharge roller 40 for discharge are provided. The sheet material P on which the toner image is fixed is guided to the discharge roller 40 by the guide member 48, and the discharge roller. 40 discharges the sheet material P to a discharge tray 42 formed on the upper surface of the housing 12.

  In the image forming apparatus 10 configured as described above, an image is formed as follows.

  First, the charging roller 26 to which a voltage is applied uniformly negatively charges the surface of the photosensitive member 22 with a predetermined charging portion potential.

  Subsequently, exposure is performed by the optical scanning device 14 so that an image portion on the charged photosensitive member 22 has a predetermined exposure portion potential, and an electrostatic latent image is formed.

  That is, an electrostatic latent image corresponding to the image information is formed on the photosensitive member 22 by turning on and off the laser emitted from the optical scanning device 14 based on image information supplied from a control device (not shown).

  Further, a developing bias set in advance for each color is applied to the developing roller 20 of the developing device 24, and the electrostatic latent image is developed with toner when passing through the position of the developing roller 20, and visualized as a toner image. The

  Therefore, the sheet material P passes through the image forming unit 60 between the photoreceptor 22 and the transfer roller 30, and the toner image is transferred to the sheet material P. The transferred toner image is heat-pressed and fixed on the sheet material P by being nipped and conveyed between a fixing roller 38A and a pressure roller 38B provided in the fixing device 38.

  Further, the sheet material P on which the toner image is fixed is guided by the guide member 48 and is discharged by the discharge roller 40 to the discharge tray 42 formed on the upper surface of the housing 12.

  Next, the fixing device will be described in detail.

  As shown in FIG. 3, the fixing device 38 is provided with a pressure roller 38 </ b> B that is rotatably supported by a casing 70 (see FIG. 5) so as to press the sheet material P. The pressure roller 38B is urged by a spring (not shown) to a fixing roller 38A disposed opposite to the pressure roller 38B to form a nip portion 62 with the fixing roller 38A.

  The fixing roller 38A is driven to rotate by the rotational force of the motor. When the fixing roller 38A is rotated in the direction of arrow D in the figure, the pressure roller 38B is driven to rotate in the direction of arrow E, and the nip portion 62 is rotated. The sheet material P that has reached is held and conveyed. Further, a halogen lamp (not shown) as a heating element is built in the fixing roller 38A, and the surface of the fixing roller 38A is kept at a predetermined temperature.

  Further, a separation claw 64 constituting a sheet material separation device 44 that separates the sheet material P from the fixing roller 38A is provided in contact with the fixing roller 38A. Specifically, when viewed from the rotation axis direction of the fixing roller 38A, the tip end portion 64A of the separation claw 64 that contacts the fixing roller 38A is tapered, and a cylindrical shaft member 72 is provided at the rear end portion. Yes. Both ends of the shaft member 72 are rotatably supported by a housing 70 (see FIG. 5), and the shaft member 72 is provided with a torsion spring (not shown). The tip portion 64A is urged against the surface of the fixing roller 38A by the spring force of the torsion spring. In the present embodiment, as shown in FIG. 4, five separation claws 64 are provided. Note that the number of separation claws 64 is not limited to five, and may be five or more and five or less.

  Further, as shown in FIG. 3, a flat sheet material guide 74 extends in the axial direction of the fixing roller 38A and is fixed to the housing 70 (see FIG. 5) above the separation claw 64. The sheet material P separated from the fixing roller 38A by the separation claw 64 is guided toward the guide member 48 (see FIG. 5).

  Further, a plate-shaped separation guide 66 is provided between the separation claw 64 and the nip portion 62 with a clearance from the fixing roller 38A, and is fixed to the housing 70 (see FIG. 5) extending in the rotation axis direction.

  More specifically, the separation guide 66 is disposed with a fixed gap of 2 mm between the fixing roller 38A and the opposite edge portion 66A of the separation guide 66 facing the fixing roller 38A. The gap between the separation guide 66 and the facing edge portion 66A is not limited to 2 mm.

  Further, as shown in FIG. 4, in the central portion in the rotation axis direction of the fixing roller 38A, the separation guide 66 is formed with a triangular convex portion 66B toward the upstream side in the conveyance direction of the sheet material P. .

  With this configuration, the sheet material P to which the toner image has been transferred is pressed against the fixing roller 38A by the pressure roller 38B when passing through the nip portion 62, and the toner on the sheet material P is heated by the heat of the fixing roller 38A. It is melted and fixed to the sheet material P.

  As shown in FIG. 2, when the toner is melted and the sheet material P rotates together with the fixing roller 38A in close contact with the surface of the fixing roller 38A, the sheet material P is separated from the separation guide 66 and the fixing roller 38A. The leading end of the sheet material P hits the leading end portion 64A of the separation claw 64, and the sheet material P is separated from the fixing roller 38A along the tapered shape of the leading end portion 64A, along the sheet material guide 74. It is conveyed upward.

  Further, as shown in FIG. 1, the stiff sheet material P, which has been conveyed with its leading end floating from the surface of the fixing roller 38A, is separated from the fixing roller 38A by the separation guide 66 and conveyed upward. Specifically, the sheet material P is smoothly separated from the fixing roller 38A gradually along the triangular hypotenuse from the leading end portion of the sheet material P reaching the convex portion 66B of the separation guide 66 shown in FIG.

  That is, in the case of thick paper, etc., which is stiff, the front end of the sheet material P may float from the surface of the fixing roller 38A due to the rigidity of the sheet material P itself, although it is affected by the printing density. Since the sheet material P with the leading end floating in this way is separated from the fixing roller 38A by the separation guide 66 arranged with a gap from the fixing roller 38A, the leading end of the sheet material P floating from the fixing roller 38A is separated. There is no collision with the separation claw 64. Further, even if the leading end of the sheet material P floating from the fixing roller 38A collides with the separation guide 66, the vibration caused by the collision force reaches the surface of the fixing roller 38A due to the gap provided between the fixing roller 38A. There is no.

  Therefore, as shown in FIG. 6, the leading end portion of the sheet material P collides with the separation claw 64, and the leading end portion 64A of the separation claw 64 prevents the damage to the fixing roller 38A such as biting into the surface of the fixing roller 38A. be able to.

  In addition, since the convex portion 66B is formed at the central portion in the rotation axis direction of the fixing roller 38A, the sheet material P can be gradually separated from the fixing roller 38A in a balanced manner. Further, by gradually separating the sheet material P, it is possible to prevent the sheet material P from colliding with the separation guide 66 at a time and causing a paper jam.

FIG. 5 is a cross-sectional view illustrating a fixing device according to an exemplary embodiment of the present invention, in which a sheet material with a leading end floating from a fixing roll is separated by a separation guide. FIG. 3 is a cross-sectional view illustrating a fixing device according to an exemplary embodiment of the present invention, in a state where a sheet material in close contact with a fixing roll is separated by a separation claw. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. FIG. 3 is a perspective view illustrating a fixing roller, a separation guide, a separation claw, and the like according to an embodiment of the present invention. 1 is a schematic configuration diagram of an image forming apparatus including a fixing device according to an embodiment of the present invention. FIG. 10 is a cross-sectional view showing a fixing device not provided with a separation guide as a comparative example of the present invention.

Explanation of symbols

10 Image forming apparatus 38B Pressure roller (Pressure member)
38A fixing roller 38 fixing device 44 sheet material separating device 62 nip portion 64 separation claw 66 separation guide 66B convex portion

Claims (5)

A sheet material separating device provided in a fixing device, comprising: a pressure member that pressurizes a sheet material; and a fixing roller that forms a nip portion with the pressure member and heats and fixes a toner image on the sheet material. ,
A separation claw that contacts the fixing roller and separates the sheet material from the fixing device;
A plate-like separation guide disposed with a gap between the fixing roller and the nip portion;
A sheet material separating apparatus.   The sheet material separating apparatus according to claim 1, wherein a convex portion is formed in the separation guide toward the upstream in the conveying direction of the sheet material.   The sheet material separating apparatus according to claim 2, wherein the convex portion is formed at a central portion in the rotation axis direction of the fixing roller.   The sheet material separating apparatus according to claim 2, wherein the convex portion has a triangular shape.   An image forming apparatus comprising the sheet material separation device according to claim 1.

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